Hi Don,

I'd just like to double-check something. It seems that you would then
agree that the SBIG AO-7 "adaptive optics" unit -- a tip-tilt mirror --
is truly "adaptive" optics. Is that right? I've asked this of others
working in the field -- astronomers and optical engineers -- and get
varied responses. Some say tip-tilt is "adaptive", others (a minority,
I think) say it's not. Most, however, give me a quizzical look and say
something like "Well, you could say..." (fill in the blank). So I'm
very interested in the view of someone not just building a particular
unit or using AO but having spent many years in the business.

Best regards,

Mike Simmons

Don Bruns wrote:

Ante Perkovic wrote:
Hi,

Can someone explain me the difference between active and adaptive optics?

"Active optics" usually refers to optics that can be slowly moved, while
"adaptive optics" usually refers to optics that can compensate
atmospheric turbulence. Active optics can range from a
temperature-programmed focuser to automatic primary recollimation to
compensate tube sag as the telescope is pointed at different altitudes.
Flexing a spherical primary to a parabolic shape as the temperature
changes can be considered active optics. "Adaptive optics" usually uses
light from the target area to determine the effects of atmospheric
turbulence, then moves the optics rapidly to compensate. These optics
may be a tip-tilt mirror or a deformable mirror.

Don Bruns